This application relates generally to actuators, and more specifically to actuators for positioning flight control surfaces in aircraft.
In order to achieve the ultra-high reliability necessary for a flight control system in an aircraft, such as a helicopter, a triplex actuator (three separate actuators connected to each output for redundancy) is required. This type of system is necessary in case any one or two of the actuators fails, the aircraft will remain under control. If simple ball screw actuators (or rotary geared actuators) are used in the triplex actuator, a jam by one actuator would prohibit the other actuators from moving. This failure mode has historically been accommodated by providing mechanical disconnects or clutches to segregate a faulty actuator. These additional mechanical components not only increase the size, cost, and complexity of the system, the additional mechanical components also provide another possible source of failure.